Żyliński, Paweł. “Orthogonal Art Galleries With Holes: A Coloring Proof of Aggarwal’s Theorem”. The Electronic Journal of Combinatorics 13, no. 1 (March 7, 2006): R20. Accessed March 15, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v13i1r20.